Endogenous opiate polypeptides and various psychological measurements of related to the stress and pain involved in childbirth are examined in 50 women patients with normal uncomplicated pregnancies. Plasma levels of beta-endorphins and corticotropin taken in late pregnancy, early labor, late labor, and postpartum are correlated with obstetrical and psychological variables including stress measurements and personality profiles indicative of low subjective discomfort, high pain threshhold, low objective levels of anxiety, and effective psychological preparation for labor.